来自破解上的一道逻辑题 麻烦大家帮忙指点

wjk

Most of the world's supply of uranium currently comes from mines.It is possible to extract uranium from seawater, but the cost of doing so is greater than the price that uranium fetches on the world market.Therefore, until the cost of extracting uranium from seawater can somehow be reduced, this method of obtaining uranium is unlikely to be commercially viable.

Which of the following would it be most useful to determine in evaluating the argument?

(A) Whether the uranium in deposits on land is rapidly being depleted

(B) Whether most uranium is used near where it is mined

(C) Whether there are any technological advances that show promise of reducing the cost of extracting uranium from seawater

(D) Whether the total amount of uranium in seawater is significantly greater than the total amount of uranium on land

(E) Whether uranium can be extracted from freshwater at a cost similar to the cost of extracting it from seawater
答案：A
A我后来自己思考了一下，可以理解，是不是因为如果陆地上U的储藏量正在急剧减少的话，有必要从海里提取U？这样这个方案就可行了？
我当时自己做的时候选的是C 我个人认为如果从海水中提取U的成本能够降低的话，不也能说明采取这个方案是可行的嘛
我对C的理解错在哪里 求指教！ 感激不尽啊～